There are more
organisms prematurely bumped off by well-meaning koi keepers than you would believe; far
more than if nothing was added to their water. Dear Reader, and water garden enthusiast,
don't let this happen to you. There are few chemical treatments that have a wide range of
safety and effectiveness; one notable exception are products made of the element copper.

Copper in various
formulations is useful in continuous, low doses as an algicide and epizoitic
(parasiticide). Used properly it is safe and effective; copper is the only EPA approved
algicide for use in potable waters. It is also one of the most common active ingredients
in the field of therapeutics in aquaristics.

Two Difficulties To Consider in
Using Copper:

Range of useful concentrations:

Though it does not mal-effect
true plants, some fishes, like koi and trout are sensitive to low levels of copper; most
invertebrates can tolerate extremely little.

Free copper-ion
availability must be present within a narrow range (0.03 to 1.0ppm, depending on species,
concentration present, physical and chemical make-up of the water and system) to be
effective and safe.

Precipitation of Copper:

Leaving solution by
settling out can be a problem, especially in hard, alkaline waters. Towards the ends of
reducing these difficulties, copper compounds are sequestered and chelated in a few
formulations; ethanol-amine complexes (e.g. cutrine), citric acid, as well as
"raw" copper sulfate pentahydrate solid and solutions.

Bonding copper
treatment extends inter-treatment intervals by supplying a physiological dose of copper
ion over a longer period of time, much the same as the use of stabilizing conditioner with
chlorine sanitizer.

Toxicity and Use:

The normal, target
concentration of copper in biological systems is @ 0.3ppm free copper to a low
range of 0.1 ppm free copper. The word "free" is emphasized as some
assays for copper measure bound copper that is not available as biocide. An artificial,
high reading may be measured using these test kits, therefore know which type of test kit
and copper you are measuring.

For non-biological
systems a continuous reading of 1.0 ppm is enough to assure effective algae control; more
is superfluous and may damage finishes and equipment.

pH Effects:

At pH's below 7.0,
the toxicity of copper is greatly enhanced. For this reason, among others, frequent
partial water changes, dilution of organics, checking and adjusting pH prior to copper
treatment, if necessary, is warranted. Regular, routine maintenance and checking of water
chemistry assures that the proper amount of free copper is present, without premature
absorption or precipitation.

Hardness:

The effectiveness
of copper decreases as water hardness increases. A significant reduction occurs when the
bicarbonate alkalinity exceeds 150 ppm as calcium carbonate. Conversely, toxicity to fish
decreases as alkalinity increases. I mention this phenomenon not so much that you should
try to manipulate hardness, but that you be aware of it's effects with copper.

Oxygen
Concentration:

One of the earliest
effects of having administered too much copper is apparent fish hypoxia, the loss of
ability to use oxygen. Common symptoms of initial acute toxicity are fish gasping,
disoriented (ataxic) at the surface, due to copper's hemolytic (blood cell splitting) and
mucus-producing effects. Copper is a proteinaceous precipitant; that is, it causes your
fish to produce more mucus. This may aid the in the suffocation or sloughing off of
parasites, but also interferes with respiration through their skin and gills. The edge:
use copper only where adequate aeration, crowding is not problematical.

Temperature and
Light; Timing Copper Administration:

Copper is almost
ineffective at temperatures below 60 degrees F. and likewise more algicidal when algae are
at their most active metabolically. Sunny days between 10:00 and 2:00 are optimal
treatment times. Overcast or murky waters are contraindicated; wait till it's warm and
sunny to apply copper.

Toxicity to
Livestock:

Koi carp begin show
signs of copper-effect at @ 0.03 ppm and may be killed under various circumstances as
elucidated above, at near the target concentration.

Other species of
"native" fishes; trout, sunfishes, catfish are even more sensitive, dying near
concentrations near 0.10 ppm. Most desirable aquatic plants are unaffected at these doses.
Note label precautions on application & rates due to different species' sensitivities.

Application:

For large,
lake-size systems copper sulfate, with or without additives, crystals or granular may be
spread by hand or equipment. Large crystals can be burlap-bagged and towed behind a boat.

For smaller water
gardens solutions may be distributed as copper-alkano-amine complexes (e.g. Cutrine) and
other chelated formulations below or above water by sprayer or watering can. Use system
water as a carrier. These compounds are safer to use with fish than "raw" copper
sulfate.

Use Precautions:

For aerial
distribution, I'd wear goggles to avoid contact with eyes, and flush with water if skin
contact occurs. It is suggested that you wear gloves and avoid breathing copper dust.
There is a very low toxicity to humans; there may be 1.0 ppm or more free copper in your
drinking water.

Corrosiveness:

Copper is very
corrosive to metals; rinse equipment three times with fresh water and other materials that
come in contact (e.g. truck beds).

Storage of Copper
Treatments:

Dry compounds are
hygroscopic; they get "lumpy" if exposed to the air. Keep dried copper compounds
in rolled bags, out of moistures way, stored in a locker. Copper Sulfate (CuSO4) is also
considered a strong oxidizer; dry products must be stored away from solvents and other
petroleum products.

Chronic to Acute
Toxicity:

Precipitated copper
may come back dangerously into solution in toxic concentration with a change in chemical
and physical conditions. Toxicity can be important in situations where the bottom detritus
is stirred up, pH lowered, water softened, oxygen concentration lowered, and/or
temperature elevated. In particular a sudden to chronic lowering of pH coupled with water
softening and/or raising of temperature may cause re-release of "lost", bound
copper, with disastrous results. The edge: once again, frequent, partial, continuous water
quality maintenance (you) will preclude this disaster.

Steps to Using Copper:

1) Measure, know the total
gallonage of system, species make-up, treatment mode, concentration for system.

3) Vent, vacuum otherwise treat the
system to remove organics, adjust water quality.

4) Treat system as outlined. For
example, with no readable copper level 1 oz. or 20 mls. of cutrine per 2000 gallons will
produce 0.30 ppm free copper initially. This is at the high end for biological systems.

Due to the efficacy of use; measure
and treat frequently at lower concentrations to provide enough free copper continuously.
If a system "gets away from you" and generates an algal bloom it may be
necessary to dump it initially or treat in another way at first.

Conclusion:

Copper compounds in various
applications do have their place as algicides, parasite controls and anti-fouling agents.
Their use is not without difficulties however. Consideration must be made for the
chemical, physical and biological make-up of the intended treatment system. Though safety
margins are sometimes small, copper is and appears will continue to be a relatively safe
and useful element in biological systems. Use it knowledgeably and with frequent testing.